The invention pertains to a machine tool for processing workpieces with tools, wherein the machine tool has a spindle housing that contains a spindle shaft and accommodates at least one tool as well as a drive device that causes a rotational movement of the spindle shaft.
Machine tools of this type are known. They contain a spindle shaft that is arranged in a housing and transmits a drive torque to a tool. The spindle shaft is driven by an electric motor, the drive shaft of which transmits a drive torque to an angular wheel that is connected to the spindle shaft in rotational play via a gear. The angular wheels that transmit the drive torque to the spindle shaft must be very exactly aligned relative to one another so as to keep their wear, the heating of the drive train and the components located next to the drive train as well as the noise of the machine tool to a minimum. In this respect, the precise axial-spacing of the angular wheels is particularly important because an excessively large or excessively small axial distance results in high wear and, in certain instances, damage to the drive train. However, this requires a significant expenditure with respect to the manufacturing technology. A lubricating oil supply that requires a separate conduit system also must be provided in order to lubricate the angular wheels.
The invention is based on the objective of developing a machine tool of the initially mentioned type that has a simple design and that can be inexpensively manufactured and easily serviced.
This objective is attained with a machine tool for processing workpieces with tools, having a spindle housing that contains a spindle shaft and accommodates at least one tool, and having a drive device that causes a rotational movement of the spindle shaft. This machine tool is characterized by the fact that the drive device contains a hydraulically operated displacement machine. Due to the operating medium circuit or conduit system required for operating the displacement machine, no additional lubricating oil circuit is required. The preferred operating medium for the displacement machine is hydraulic oil with superior lubricating and cooling properties, wherein any incompressible medium may, in principle, be used. The lubrication and the cooling of the moving parts arranged in the spindle housing are simply carried out by the existing hydraulic oil supply of the displacement machine such that the manufacturing costs of the machine tool are reduced. In addition, a displacement machine arranged in a stable housing only produces low running noises, i.e., the operating noise is also reduced. A drive device that contains a displacement machine has a simple design and is operationally very safe. In addition, such a drive device practically requires no maintenance due to the very low wear. Consequently, the manufacturing and operating costs of the machine tool are very low. In addition, relatively large tolerance ranges can be realized, e.g., with respect to the arrangement of the hydraulic conduit system. Consequently, the manufacturing expenditure is relatively low.
One preferred embodiment of the machine tool is characterized by the fact that the drive device is exclusively formed by the displacement machine. A gear that transmits the drive torque and different speeds to the spindle shaft is not required if a displacement machine is utilized as the drive device. In order to influence the speed, the volume flow introduced into the displacement machine need only be varied or correspondingly adapted, wherein the pressure of the incompressible medium is varied or correspondingly adapted in order to change the drive torque. The constructive expenditure for such control of the speed and the drive torque is relatively low, i.e., the cost of the machine tool is reduced.
According to one particularly preferred embodiment of the machine tool, the drive device is realized in the form of an axial piston machine, in particular, a swash-plate machine, that has high power in relation to its structural dimensions. In this case, the speed of the drive shaft can be simply varied by means of an adjustable angular block that changes the displacement volume of the piston. A compact machine tool with small dimensions can be realized due to this reduction of the required structural space.
In another preferred embodiment of the machine tool, the drive device and the spindle housing form a drive unit. The drive device may be flanged onto or integrated into the spindle housing such that a particularly compact structural shape is attained. The spatial distance between the drive device and the spindle housing is, due to the design of the drive unit, so small that power/torque transmission elements, e.g., gears, articulations or the like, can be eliminated. This is possible because the spindle shaft replaces the driven shaft of the drive device and is directly driven by this drive device. Due to the elimination of drive train components which transmit forces and are subject to wear, the spindle shaft can be driven practically without slip. In addition, this drive unit is characterized by a compact, modular design and a relatively low running noise. The running noise is, in particular, reduced by a stable spindle housing and/or a stable housing of the drive unit such that the noise level caused by the machine tool is reduced. Due to the combination of the spindle shaft and the drive unit, the constructive expenditure as well as the expenditure with respect to the manufacturing technology are relatively low, i.e., the manufacturing costs are correspondingly reduced.
Another particularly preferred embodiment of the machine tool is characterized by the fact that the drive unit can be inserted into a spindle head that carries several drive units. Different tools are usually arranged on such a spindle head. The spindle head is used, for example, in automated manufacturing machines, e.g., in a CNC-controlled milling machine. Due to the modular design of the spindle housing and the drive device, a tool change can be carried out very fast such that the down time of the machine tool is significantly reduced. In addition, a drive device with a different speed or power can be provided for each tool, wherein the respective drive devices are adapted to the operating specifications of the respective tool. Thus, the control expenditure for the machine tool can be significantly simplified.
Additional advantageous embodiments are disclosed in the remaining subordinate claims.